Variable inductance



Aug. 16,1927. 1,639,044

, G. F. MANSBRIDGE VARIABLE INDUCTANCE Filed Auml@ i924 George /l idgePatented Aug. 16, 1927.

UNITED STATES 1,639,04@ PATENT oFFl'cE.

GEORGE FREDERICK MANSBRIDG, F NEW BRNET, ENGLAND.

VARIABLE INDUCTANGE.

Application led August 16, 1924, Serial No. 732,531, and in GreatBritain August 27, 1923;

This invention relates to variable inductances similar to those shownand described in the specification of United States Letters Patent No.893,340 of 1908k granted to me.

Variable inductances as heretofore proposed possess certain defects,chief among),- which are (a) their restricted range of variation, (o)their electrostatic capacity and (c) their bulkiness and inconvenientshape. Now, it

is the object of this invention to remove these defects and to obtain ina small and convenient form a variable inductance having a large vrangevofvariation and a small electrostatic capacity. v

According to this invention the inductance elements are `made of D-form,or substantially so, as explained in the aforesaid patent specificationandwound so that their self Capacity is minimized. This I do by windingin a single layer with space between each convolution and the next or byone of the well known anti-capacity methods e. g.

that known as basket winding or I may employ two-layer or multi-layerwindings wound in cellular, openwork, or other well known anti-capacityform. The inductance elements so prepared are mounted on discs in suchmanner that the mountings and their inductance elements can be rotatedrelatively to one another in order to vary the inductance.

In order that this invention may be the more clearly understood andreadily carried into effect, I will proceed to 'describe the same withreference to the accompanying drawings, which illustrate by way ofexample, and not of limitation, the preferred embodiment of thisinvention, and wherein- Figure l is a plan of the bottom disc 40 showingthe inductance elements mounted therein, and

Figure 2 is an under plan of the top disc also showing the inductanceelements mounted therein.

Figures 3 and 4 are under plan and plan respectively of the parts of theinstrument as assembled.

Figure 5 is a section on line 5-5 of Figure 3.

Figure 6 is an elevation of the instrument.

Referring to the drawings, the instrument comprises two discs a and b,preferably of ebonite or like insulating material. Mounted in the disc aare two kidney-shaped inse ductance elements c and d sunk slightly be-`low the outer vedge of the dise a and wound so as to have a lowself-capacity. These elements are wound in opposite directions andtheouter end of element c is joined to the inner end of the element d.The inner end of the element c is connected to a terminal c1 mounted onthe underside of the disc a, and the outer end of element d is connectedto a like terminal (Z1. The disc a is provided ywith supporting legs al.

In thedisc o are arranged two inductance elements e and f which areshaped, wound and arranged similarly to the inductance elements c and CZwhich have their inner ends joined together. The outer ends of theseelements are joined ate1 and f1 to flexible leads c2 'and f2respectively. The leads pass through a Vmetal plug g fixed to the disc oand the saidy plug is insulated from the inductance'elements'by aninsulating sleeve g1. The lower portion of the plug is rotatably mountedin a bushing a2 fixed in the disc a, and a nut g2 is screwed on to thelower extremity of the plug to 'keep the discs together.

The free ends of the flexible leads e and f2 are attached to terminalse3 and f3 mounted on the underside of the disc a.

By sinking in the inductance elements, as above described, I obtain theoptimum position of thebest balance between maximum inductive effect andminimum capacity between the inductance elements on one dise and thoseon the other.

The upper edge of the disc a is provided with an upstanding lip a3adapted to take into a circumferential recess, o1, formed in the loweredge of the disc o. vThe recess b1 is of such length that, inconjunction with the lip a3, it limits the rotary movement of one discrelatively to the other to 180".

To the top of the disc o is vulcanized or otherwise secured a boss b2having a bevelled edge whereon is inscribed a scale of 180o which, inconjunction with a line marked on a pointer 7L, secured to the disc a,indicates the angle through which the top disc has been rotated in orderto vary the inductance. The rotation of the disc b is effectedby meansof a knob o3 which is fixed on a rod o", screwed into the plug Strips ofmetal may be provided to form connections between the terminals 01, d1,e3 and f3 so as to connect the inductance elements c and d and e and feither in series for high values or in parallel for low valuesu will bereadily 'understoodthat by' ro-f any other suitable known methoddesigned to give low self-capacity.

According to a modiieation, the induetance elements areembetlded in anysuitable known substance having a low dielectric con- '7 stant.

To increase the range of variation the in duotanee elements may be Woundin two or more sections and. means may be provided Whereb one or more ofthe sections may conveniently be cut out of circuit(l In some eases theinductance elements may be of D-shape having the straight sides of eachpair arranged contiguously, or they may be of circular or other thankidney shape.

Thus',A by this invention the advantages o f large range variability ofvinductance, conjointly with eornpactness of construction and, lowelectrostatic capacity are obtained.

I claim:-

In ai variable induo'tance, an u )per (lise having a partiallyoircumferentia 'groove, a lower dise having terminals on its undersideand an unstanding stop, tivo substantialIy kidney-Shaped inductanceelements in each disc, a bushing in the lower disc, a metal plug carriedby the upper dise and passingr through the bushing in the lower dise,Hexible connections from the induetanee elements in the upper disepassing through the said plug to eert-ain of the terminals on thevunderside of the lower dise, connections from the inductance elementsin the lower dise te other of the said terminals, temporary switchmembers to bridge the said terminals so as to Connect the saidinduetanceelement-s either in series or in parallel at Will, thearrangement beinU` such that the said stop abuts against the end of thegroove in the upper dise and limits the relative rotar movement of thetwo discs to 180.

n testimony whereof I have signed my name to this specification.

GEUKGE FREDERICK MANSBRIDGE.

